CN204376517U - A kind of bidirectional DC-DC converter for direct current network energy storage - Google Patents

Abstract

The utility model relates to a bidirectional DC-DC converter for DC power grid energy storage, which consists of a L _i C _i (i=1, 2...n) filter unit, a half bridge circuit, a network side inductance L and a network side The filter capacitor C is combined; its circuit includes N filter inductors L ₁ , L ₂ ... L _n ; N filter capacitors C ₁ , C ₂ ... C _n ; 2N high-frequency power switch tubes T _1u , T _2u ... T _nu and T _1d , T _2d ... T _nd and 2N diodes D _1u , D _2u ... D _nu and D _1d , D _2d ... D _nd in antiparallel connection with the high-frequency power switch tube; one grid side filter inductor L and capacitor C. The lower bridge arms of each half-bridge circuit are serially connected in series with the grid side filter inductor L and then connected to the DC power grid in parallel with the grid side filter capacitor C; the two ends of the bridge arms of each half bridge circuit are connected to the super single capacitor. The converter can be used in the occasion of high-voltage and high-power energy storage. Under the same power condition, the voltage and current stress of the switching device of the bidirectional DC-DC converter are small, and the storage and feedback of DC electric energy can be realized.

Description

A Bidirectional DC-DC Converter for Energy Storage in DC Grid

technical field

The utility model belongs to the field of power electronics, and in particular relates to a bidirectional DC-DC converter used for energy storage of a direct current grid.

Background technique

With the rapid consumption of traditional fossil energy (such as oil, coal, natural gas, etc.), and the increasing problems of the world's energy crisis and environmental pollution, the rational development and utilization of green renewable energy has become an urgent need for human beings. . For renewable energy, solar photovoltaic power generation, wind power generation and fuel cell power systems have received more and more attention, and how to connect these new energies to the grid for power generation and transform them into electric energy that users can directly use is a distributed The main research directions in the field of power generation. Energy storage devices play a vital role in distributed renewable energy grid-connected power generation systems. In order to solve the voltage level mismatch between the low voltage of energy storage devices in parallel and the high voltage required for grid connection, it is necessary to use High voltage and large capacity bidirectional DC-DC energy storage converter.

Supercapacitor is an important energy storage element, which has the characteristics of high power density, high charge and discharge efficiency, and long cycle life. It has broad application prospects in microgrid systems, new energy power generation, and braking energy absorption and utilization systems. In high-voltage, large-capacity supercapacitor energy storage applications, due to the low voltage of energy storage capacitor cells (or components connected in series with capacitor cells), it is usually necessary to form a system by connecting multiple cells or components in series. However, the discrete parameters of supercapacitor single components are relatively large, and the system in which multiple monomers are directly connected in series needs to consider the problem of voltage balance.

Utility model content

In view of this, the utility model provides a bidirectional DC-DC converter for energy storage of a DC power grid, which can be applied to high-voltage and large-capacity energy storage occasions.

The utility model is realized through the following technical solutions: a bidirectional DC-DC converter for DC power grid energy storage, which is characterized in that it consists of an LC filter unit, a half-bridge circuit, a network-side inductance L and a network-side filter capacitor C combined; the bidirectional DC-DC converter includes n filter inductors L ₁ , L ₂ ... L _n ; n filter capacitors C ₁ , C ₂ ... C _n ; 2n high-frequency power switch tubes T _1u , _{One _ _ _ _ _ _ _ _ _ _} The grid-side filter inductor L and capacitor C; the lower bridge arm of the half-bridge circuit is serially connected in series with the grid-side filter inductor L and then connected to the DC grid in parallel with the grid-side filter capacitor C; the bridge arm of the half-bridge circuit The two ends are connected to the supercapacitor monomer through the filtering unit.

The beneficial effect of the utility model is that it can help to reduce the contradiction between the low voltage of the supercapacitor monomer and the high voltage of the application occasion, and the voltage and current stress of the switching device of the bidirectional DC-DC converter are adopted under the same power condition Small, the required inductance under the same output current ripple condition is only 1/N ² of the single half-bridge topology (N is the number of cascaded modules), etc., which has advantages in high-voltage, high-power bidirectional power conversion occasions.

Description of drawings

Fig. 1 is a circuit schematic diagram of a bidirectional DC-DC converter used for energy storage of a DC power grid provided by the utility model.

Fig. 2(a) and (b) are the current path diagrams under the energy storage state of the super capacitor of the bidirectional DC-DC converter of the present invention.

Fig. 3(a) and (b) are the current path diagrams in the energy-discharging state of the supercapacitor in the bidirectional DC-DC converter of the present invention.

Detailed ways

The preferred embodiments are described in detail with reference to the accompanying drawings.

Fig. 1 is a circuit schematic diagram of a bidirectional DC-DC converter for DC grid energy storage. Its circuit is composed of LC filter unit, half-bridge circuit, grid-side inductor L and grid-side filter capacitor C; among them, the bidirectional DC-DC converter has n filter inductors L ₁ , L ₂ ... L _n ; n filter inductors Capacitors C ₁ , C ₂ ... C _n ; 2n high-frequency power switching tubes T _1u , T _2u ... T _nu and T _1d , T _2d ... T _nd and 2n high-frequency power switching tubes antiparallel diodes D _1u , D _2u ... D _nu and D _1d , D _2d ... D _nd ; a grid-side filter inductor L and capacitor C; the lower bridge arm of the half-bridge circuit is serially connected in series with the grid-side filter inductor L Then connect to the DC power grid in parallel with the grid-side filter capacitor C; the two ends of the bridge arm of the half-bridge circuit are connected to the supercapacitor monomer through the filter unit.

Fig. 2(a) and (b) are the current path diagrams under the energy storage state of the super capacitor of the bidirectional DC-DC converter of the present invention. When the supercapacitor bank is in the energy storage state, the bidirectional DC-DC converter works in the boost mode. The half-bridge module’s lower-bridge switch tube T _id , upper-bridge diode D _iu and inductor L form a Boost converter. The DC bus side Energy is transferred to the supercapacitor. According to the turn-on and turn-off of the switch tube T _id , the circuit is divided into two modes. Mode 1 is shown _in Fig. The conduction of _id is transferred to the grid-side inductance L; mode 2 is shown in Figure 2(b): when the switch tube T _id is turned off, the energy of the DC bus and the grid-side inductance L follows the conduction of the freewheeling diode D _iu The pass is filtered and transferred to a supercapacitor bank. where i=1, 2...n.

Fig. 3(a) and (b) are the current path diagrams in the energy-discharging state of the supercapacitor in the bidirectional DC-DC converter of the present invention. When the supercapacitor bank is in the energy-discharging state, the bidirectional DC-DC converter works in step-down mode. The upper-bridge switch T _iu , the lower-bridge diode D _id and the inductor L of the half-bridge module form a Buck converter. The supercapacitor bank The energy is transferred to the DC bus side. According to the turn-on and turn-off of the switch tube T _iu , the circuit works in two modes respectively. Mode 1 is shown in Fig. 3(a): when the switch tube T _iu is turned on, the energy of the supercapacitor C _si is filtered Inductor L _i and switch tube T _iu are transferred to the grid-side inductor L, filter capacitor C and DC bus; mode 2 is shown in Figure 3(b): when the switch tube T _iu is turned off, the energy of the grid-side inductor L varies with The conduction of the freewheeling diode D _id is transferred to the filter capacitor C and the DC bus. where i=1, 2...n.

Claims (1)

1. A bidirectional DC-DC converter for DC grid energy storage is characterized in that it is composed of an LC filter unit, a half-bridge circuit, a grid-side inductance L and a grid-side filter capacitor C; the bidirectional DC-DC The changer includes n filter inductors L ₁ , L ₂ ... L _n ; n filter capacitors C ₁ , C ₂ ... C _n ; 2n high frequency power switch tubes T _1u , T _2u ... T _nu and T _1d , T _2d ... T _nd and 2n diodes D _1u , D _2u ... D _nu and D _1d , D _2d ... D _nd in antiparallel connection with the high-frequency power switching tube; a grid-side filter inductor L and capacitor C; The lower bridge arm of the half-bridge circuit is connected in series with the grid-side filter inductor L in series and then connected to the DC power grid in parallel with the grid-side filter capacitor C; the two ends of the bridge arm of the half-bridge circuit are connected to a super capacitor unit through a filter unit body.